Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of the claimed design;

FIG. 2 is a front view showing a second image thereof; and,

FIG. 3 is a front view showing a third image thereof.

The appearance of the transitional image transitions between the imagesshown in FIGS. 1-3. The process or period in which an image transitionsto another image forms no part of the claimed design.

The gradient background of the graphical user interface is claimedsubject matter.

The longer broken-line showing of a portion of an electronic device andthe intermediate-length broken-line showing of a display screenboundary, as well as the features within the interface shown in stillshorter broken-lines, are included for the purpose of illustratingenvironmental structure and form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof withtransitional graphical user interface, as shown and described.